Holmes & Watson is a 2018 mystery comedy film written and directed by Etan Cohen. The film stars Will Ferrell and John C. Reilly as the eponymous characters Sherlock Holmes and Dr. Watson, respectively; with Rebecca Hall, Rob Brydon, Kelly Macdonald, Steve Coogan and Ralph Fiennes in supporting roles. The plot follows the famed detective duo as they set out to find the culprit behind a threat at Buckingham Palace.

First announced in 2008 with Sacha Baron Cohen as Holmes and Ferrell as Watson, Holmes & Watson languished in development hell for several years before Ferrell and Reilly were confirmed for their eventual roles in July 2016, and Etan Cohen was announced as director. Filming took place around London from late 2016 to early 2017. It is the third collaboration between Ferrell and Reilly after Talladega Nights: The Ballad of Ricky Bobby (2006), and Step Brothers (2008), and the first not to be directed by Adam McKay (who instead co-produced this film with Ferrell, Jimmy Miller and Clayton Townsend).

Holmes & Watson was released in the United States on December 25, 2018, by Sony Pictures Releasing, through its Columbia Pictures label. The film underperformed at the box office, grossing $41.9 million worldwide on a $42 million budget and was panned by critics, who lamented its poor script, dated and unfunny jokes and its squandering of the cast and source material. Some critics labelled it the worst film of 2018. The press reported numerous instances of people walking out early during screenings. The film received six nominations at the 39th Golden Raspberry Awards, and won four, including Worst Picture.